Optical information recording device

ABSTRACT

The invention provides a method effective in detecting a reproduction signal in real time correction in which correction is simultaneously performed with recording. In this method, a laser beam emitted from a laser diode  110  is divided into a plurality of beam spots by a diffraction grating  114.  One of the plurality of beam spots is used as a beam spot for recording, and another beam spot is used as a beam spot for reproduction. Reflected light components obtained from these beam spots are independently detected by a detector  122.  A period for which a recording laser beam is in an ON state is referred to as a gate signal, and a mask is put on an RF signal obtained from a beam spot for reproduction, thereby selectively detecting pits reproduced when the recording laser beam is in the ON state.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical information recordingdevice, and more particularly, to an optical information recordingdevice capable of correcting recording conditions in real time.

2. Description of the Related Art

In general, the recording of information on an optical informationrecording medium, such as an optical disk, is carried out as follows:record data is modulated in an EFM (Eight to Fourteen Modulation) manneror eight-to-sixteen modulation manner; a recording pulse is formed basedon this modulation signal; and the intensity or irradiation timing of alaser beam is controlled based on this recording pulse, thereby formingrecording pits on the optical disk.

In this manner, since the recording pits are formed by using heatgenerated by the irradiation of the laser beam, it is necessary to setthe recording pulse in consideration of a heat accumulation effect orthermal interference. Therefore, in the related art, various parametersconstituting the recording pulse are set in plural strategy formats forevery kind of optical disk, and a strategy the most suitable for therecording conditions is selected from the plural strategies, therebyrecording information on the optical disk.

This strategy depends not only on an individual device differences inoptical information recording devices, such as a variation in the spotdiameter of a pick-up device or a variation in the precision of amechanism, but also on manufacturers of optical disks used for recordingreproduction and the recording speed. Therefore, setting the optimalstrategy is to improve recording quality.

Therefore, there has been proposed a method in which the strategies themost suitable for various optical disks manufactured by differentcompanies are calculated, these strategies are previously stored in amemory so as to correspond to the respective manufacturing companies,the manufacturing company recorded on the optical disk is read wheninformation is recorded on the optical disk, and the strategy the mostsuitable for the read manufacturing company is read out from the memory.

However, according to the above-mentioned method, the optimal recordingcan be performed on the optical disks of the manufacturing companiespreviously stored in the memory, but cannot be performed on opticaldisks of manufacturing companies that are not stored in the memory. Inaddition, when the optical disks of the manufacturing companiespreviously stored in the memory are different from each other inrecording speed, the optimal recording cannot be performed.

Therefore, a method in which test recording is previously performed forevery recording condition, and in which the optimal strategy isdetermined, based on this test recording, which makes it possible tocope with various optical disks, has been disclosed in the followingrelated arts: JP-A Nos. 5-144001, 4-137224, 5-143999, and 7-235056.However, in the method disclosed therein, the test recording has to bepreformed before information recording starts. Therefore, it is notpossible to perform strategy correction at the same time as recording,and thus it is difficult to cope with a case in which the optimalconditions of the inner and outer circumferences of an optical disk aredifferent from each other.

As a result, that is, an inner circumferential portion of an opticaldisk may be slightly different from an outer circumferential portionthereof in recording characteristics, and the recording speed of theinner circumferential portion may be different from that of the outercircumferential portion in a recording apparatus. Therefore, adifference in recording quality between the inner circumferentialportion and the outer circumferential portion can occur. Thus, in orderto solve the above-mentioned problem, a technique of reducing thedifference in recording quality between the inner circumferentialportion and the outer circumferential portion by adjusting the output ofa laser has been disclosed in JP-A No. 53-050707. The above-mentionedrelated art also discloses a technique of automatically performing theoptimization of the output of a laser by detecting a variation in theamount of light of an auxiliary beam, which is called OPC.

In the above-mentioned OPC, since a unit for adjusting power isprovided, it is possible to calculate correction conditions using astatistical index, such as an asymmetric value, which makes it possibleto perform real time correction in which correction is simultaneouslyperformed with recording. However, when the width or phase condition ofa pulse is corrected, it is necessary to detect the amount of deviationbetween a recording pulse and a pit formed on an optical disk. Thus, inthe above-mentioned OPC, it is difficult to cope with the case in whichthe optimal conditions of the inner and outer circumferential portionsof an optical disk are different from each other.

Therefore, in order to correct the pulse conditions in real time, it isnecessary to detect the position or length of a pit at the same timewhen recording is performed. As an approach to cope with this, atechnique of reproducing substantially the same place as a recordingplace has been disclosed in JP-A No. 51-109851. However, this techniqueis applicable to magneto-optical recording, but is hardly applicable tooptical recording not using magnetism. That is, in the magneto-opticalrecording, since information is recorded by the variation of magnetism,the output of a laser is not modulated. However, in the opticalrecording, since information is recorded by modulating the output of alaser, there is a problem in that the modulation has an effect on areproduction side.

Techniques to solve this problem have been disclosed in JP-A Nos.1-287825, 7-129956, 2004-22044, and 9-147361. JP-A No. 1-287825discloses a technique of separately irradiating laser beams to anon-recording area and a recording area, and of acquiring reproductionsignals by performing division between the respective signals obtainedby the irradiation. According to this technique, it is possible tocorrect the distortion of a reproduction signal waveform by modulatingthe intensity of a laser beam when information is recorded.

Further, JP-A No. 7-129956 discloses a technique of obtainingreproduction signals by canceling out a modulated output by areverse-phase clock and a laser output properly amplified by auto gaincontrol (AGC).

Furthermore, JP-A No. 2004-22044 discloses a technique of canceling outthe distortion of a reproduction signal due to the waveform variation ofa recording pulse by creating a signal corresponding to the waveformvariation of the recording pulse using a delay inversion equivalentcircuit.

Moreover, according to the techniques disclosed in the above-mentionedJP-A Nos. 1-287825, 7-129956, and 2004-22044, modulation components canbe cancelled out by calculation in theory. However, these techniqueshave various problems in practical use from the viewpoint of theprecision of cancellation or the speed of calculation.

Further, JP-A No. 9-147361 discloses a technique of detecting, in realtime, the deviation of a recording state by inputting a delay pulseobtained by delaying a recording pulse, a gate signal obtained byinverting a modulated signal, and a reproduction pulse into a phasecomparator.

However, according to the technique disclosed in the above-mentionedJP-A No. 9-147361, pits are reproduced when the recording laser is in alow outputstate. Therefore, when the output of a sub-beam is low, it isdifficult to obtain a superior reproduction signal. In particular, in astructure in which sub-beams for reproduction are generated by branchinga main beam for recording, when a branching ratio is 20:1 or 30:1, thereis a problem in that the sub-beam does not have a sufficient output.

That is, in JP-A No. 9-147361, the branching ratio is set to 8:1, butthe branching ratio tends to increase with an increase in the speed ofrecording. In addition, the output of the beam is generally 1 mW orlower when the recording laser is in the low output state state.Therefore, the intensity of light reflected from a recording surfacedetectable when the recording laser is in the low output state statebecomes extremely weak. When the intensity of detectable light is weak,the light can be easily affected by a circuit noise, a media noise, etc.As a result, a superior detection signal is not obtained.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a methodeffective in detecting a reproduction signal in real time correction inwhich correction is simultaneously performed with recording.

In order to achieve the above-mentioned object, according to a firstaspect of the invention, an optical information recording device formspits on an optical recording medium by pulse irradiation of a recordinglaser beam onto the optical recording medium, and detects the pits byirradiating a reproduction laser beam onto the optical recording medium.In the optical information recording device, the pulse irradiation ofthe recording laser beam is performed based on a recording pulse havingat least two output areas, a high output segment (referred to herein asan ON state) and a low output segment (referred to herein as an OFFstate), and the detection of the pits is performed within a periodduring which the recording laser beam is irradiated in the high outputsegment.

As such, even if the reproduction laser beam is generated by thedivision of the recording laser beam, it is possible to secure theoutput of the reproduction laser beam by performing the detection of apit in the high output segment of the recording laser beam. Inparticular, the first aspect of the invention is effective when abranching ratio of the recording laser beam and the reproduction laserbeam is large and when it is difficult to supply a sufficient output tothe reproduction laser beam.

That is, since a laser beam having higher light-emitting intensity isoutput when pits are recorded rather than when normal reproduction isperformed, it is possible to detect a reproduction signal havingrelatively small amount of noise with high precision by extracting thehigh output conditions selectively to fetch the reproduction signal.

It is possible to cope with a difference in recording quality betweenthe inner and outer circumferential portions of an optical disk bycorrecting recording conditions in real time, based on the pitinformation detected in this way. In addition, the invention includes atechnique of optimizing strategy by reading out a short pit while a pitlonger than a detection target is recorded and a technique of directlyreading out information immediately after recording without suspending arecording operation to detect the deviation of a recording signal and ofcorrecting strategy based on the detected deviation.

Further, according to a second aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium. In the optical informationrecording device, the pulse irradiation of the recording laser beam isperformed based on a recording pulse having at least two output areas, ahigh output segment and a low output segment, and the pulse irradiationof the reproduction laser beam is performed at a timing synchronizedwith the pulse irradiation of the recording laser beam. In addition, thedetection of the pits is performed in the high output segment of thereproduction laser beam.

In this way, it is possible to perform high-precision signal detectionby synchronizing the reproduction laser beam with the recording laserbeam and by detecting the pits in the high output segment of thereproduction laser beam. In addition, aspects of synchronism include thebranch of a laser beam by diffraction, the irradiation of two laserbeams, and the driving of twin lasers.

Furthermore, according to a third aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium. In the optical informationrecording device, the pulse irradiation of the recording laser beam isperformed based on a recording pulse having at least two output areas, ahigh output segment and a low output segment, and the high outputsegment has a constant output portion in which the level of therecording pulse is fixed. In addition, the detection of the pits isperformed within a period for which the recording laser beam isirradiated onto the constant output portion.

Here, the term ‘constant output portion’ means an area in which therecording pulse is in an ON state and stable modulation with lessmodulation is performed, and preferably an area in which anon-modulation state is maintained longer than a predetermined time.More specifically, it is preferable to use a constant output portion of14T or 11T having a longer high output segment of the recording pulse.

As such, it is possible to avoid being affected by modulation bycarrying out pit detection of the recording pulse in the constant outputportion. That is, even if the same light source is used for recordingand reproduction, it is possible to perform the detection of a pit,based on the laser beams having a high output and a fixed output, byselectively using a stable non-modulation area in which the recordingpulse does not vary steeply. As a result, it is possible to obtain ahigh-precision signal. Moreover, according to a fourth aspect of theinvention, an optical information recording device forms pits on anoptical recording medium by pulse irradiation of a recording laser beamonto the optical recording medium, and detects the pits by irradiating areproduction laser beam onto the optical recording medium. In theoptical information recording device, the pulse irradiation of therecording laser beam is performed based on a recording pulse having atleast two output areas, a high output segment and a low output segment,and the high output segment has a constant output portion in which thelevel of the recording pulse is fixed. In addition, the pulseirradiation of the reproduction laser beam is performed at a timingsynchronized with the pulse irradiation of the recording laser beam, andthe detection of the pits is performed in the constant output portion ofthe reproduction laser beam.

As such, it is possible to detect signals with high precision bysynchronizing the reproduction laser beam with the recording laser beamand by detecting the pits in the constant output portion of thereproduction laser beam.

Furthermore, according to a fifth aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium, wherein the recordinglaser beam and the reproduction laser beam are obtained by branching alaser beam. The optical information recording device includes a pulsegenerating unit that generates a recording pulse having at least twooutput areas, a high output segment and a low output segment and a maskunit that puts a mask on a reproduction signal obtained by irradiatingthe reproduction laser beam, using the high output segment of therecording pulse.

As such, it is possible to selectively extract signals reproduced by ahigh-output laser beam by masking the reproduction signal in the highoutput segment of the recording pulse. In addition, the masking methodincludes a method of masking an RF signal obtained by the reproductionlaser beam and a method of masking a binary reproduction signal.

Moreover, according to a sixth aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium, wherein the recordinglaser beam and the reproduction laser beam are obtained by branching alaser beam. The optical information recording device includes a pulsegenerating unit that generates a recording pulse having at least twooutput areas, a high output segment and a low output segment; a unitthat specifies a constant output portion, in which the level of therecording pulse is fixed, out of the high output segment; and a maskunit that puts a mask on a reproduction signal obtained by irradiatingthe reproduction laser beam, using the constant output portion of therecording pulse.

As such, it is possible to selectively extract a signal reproduced bythe laser beam having a stable high output by masking the reproductionsignal in the constant output portion of the recording pulse.

Further, according to a seventh aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium, wherein the recordinglaser beam and the reproduction laser beam are obtained by branching alaser beam. The optical information recording device includes a pulsegenerating unit that generates a recording pulse having at least twooutput areas, a high output segment and a low output segment; a gatesignal generating unit that generates a gate signal using the highoutput segment of the recording pulse; a unit that specifies a timedifference between the recording laser beam and the reproduction laserbeam; a unit that specifies a detection target pulse having a lengthshorter than the gate signal; and a pit detecting unit that acquires areproduction signal obtained by irradiating the reproduction laser beamat the timing when the detection target pulse is included in the gatesignal in consideration of the time difference.

As such, it is possible to more reliably detect pits by selectivelydetecting a pit having a length shorter than the gate signal. That is,when a long pit is recorded, the high-output state of a laser beam ismaintained longer than when a short pit is recorded. Therefore, it ispossible to reliably acquire information on the length or phase of a pitby selectively detecting the recording pit having a recording timeshorter than the light-emitting time of the recording laser beam, usingthe reproduction laser beam, within the light-emitting time. Inaddition, the gate signal can be used as follows.

A gate signal corresponding to a recording pulse of a pit having alength longer than a detection target is prepared, and the gate signalis compared to a detection signal of a beam spot for detectingreproduction to selectively extract only a reproduction signal duringthe recording of a long pit.

In addition, a gate signal corresponding to a recording pulse of a pithaving a length relatively longer than a detection target is prepared,and the gate signal is compared to a detection signal of a beam spot fordetecting reproduction to selectively extract only a recording pulse ofa long pit.

Furthermore, according to an eighth aspect of the invention, an opticalinformation recording device forms pits on an optical recording mediumby pulse irradiation of a recording laser beam onto the opticalrecording medium, and detects the pits by irradiating a reproductionlaser beam onto the optical recording medium, wherein the recordinglaser beam and the reproduction laser beam are obtained by branching alaser beam. The optical information recording device includes a pulsegenerating unit that generates a recording pulse by calculating thelogical sum of a first pulse and a second pulse; a unit that pulseirradiates the recording laser beam, based on the recording pulse; agate pulse generating unit that generates a gate pulse by calculatingthe logical multiplication of the second pulse and an inversion signalof the first pulse; and a pit detecting unit that acquires areproduction signal obtained by irradiating the reproduction laser beam,based on the gate pulse.

As such, the gate pulse for masking the reproduction signal is generatedby using a pulse component for driving the recording laser beam. Thus,it is possible to improve the generation efficiency of a gate signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the internal structure of a driveaccording to the invention;

FIG. 2 is an exploded perspective view illustrating the structure of apick-up unit incorporated into the drive shown in FIG. 1;

FIG. 3 is a plan view illustrating the positions of spots irradiatedonto an optical disk;

FIG. 4 is a conceptual view illustrating the relationships between adetector and the spots irradiated onto the optical disk;

FIGS. 5A to 5E are conceptual views illustrating the relationshipsbetween the shape of a recording pulse and a stable area;

FIG. 6 is a circuit block diagram illustrating the internal structure ofa pulse generating circuit shown in FIG. 1;

FIGS. 7A to 7E are timing charts illustrating a generation principle ofa gate signal shown in FIG. 6;

FIG. 8 is a circuit diagram illustrating the internal structure of an LDdriver shown in FIG. 1;

FIG. 9 is a circuit block diagram illustrating the internal structure ofa mask circuit shown in FIG. 1;

FIGS. 10A to 10F are timing charts illustrating the relationships amonga recording pulse, a gate pulse, and a reproduction signal;

FIG. 11 is a conceptual view illustrating a generating process of a flagsignal executed by a CPU shown in FIG. 1;

FIGS. 12A to 12E are timing charts illustrating the relationshipsbetween a main beam for recording and a sub-beam for reproduction;

FIGS. 13A to 13G are timing charts illustrating the relationships amonga recording pulse, a pulse obtained by delaying the recording pulse, andan RF signal;

FIG. 14 is a block diagram illustrating an example of a process ofdetecting a short pit or space during the recording of a long pit;

FIG. 15 is a block diagram illustrating the relationships between acounter 256 shown in FIG. 14 and a pulse generating circuit 300 shown inFIG. 1;

FIGS. 16A to 16C are conceptual views illustrating an example of a casein which a bit string is stored in a buffer 250-2 shown in FIG. 14;

FIGS. 17A to 17C are conceptual views illustrating the variation of a 4Tspace, which becomes a detection target, during the recording of a 14Tpit;

FIG. 18 is a block diagram illustrating another example of the processof detecting a short pit or space during the recording of a long pit;

FIGS. 19A to 19G are timing charts illustrating an example of a processexecuted by a circuit block shown in FIG. 18;

FIGS. 20A to 20D are conceptual views illustrating a determinationreference of a determination signal generated by the circuit block shownin FIG. 18;

FIG. 21 is a block diagram illustrating still another example of theprocess of detecting a short pit or space during the recording of a longpit;

FIGS. 22A to 22E are timing charts illustrating an example of a processexecuted by a circuit block shown in FIG. 21; and

FIGS. 23A to 23D are timing charts illustrating an example of a processexecuted by a reset pulse generating circuit 426 shown in FIG. 21.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an optical information recording device according to theinvention will be described in detail with reference to the accompanyingdrawings. In addition, the invention is not limited to the followingembodiments, and various modification and changes of the invention canbe made without departing from the scope and spirit of the invention.

FIG. 1 is a block diagram illustrating the internal structure of a driveaccording to the invention. As shown in FIG. 1, a drive 100 performs aninformation recording or reproducing process on an optical disk 500,using a laser beam emitted from a laser diode 110 and transmits orreceives data to or from an external apparatus, such as a personalcomputer 600.

When information is recorded on the optical disk 500, record datareceived from the personal computer 600 through an interface circuit 218is encoded by an EFM encoder/decoder 216, and then the encoded recorddata is processed by a CPU 212. Then, a strategy, which is a recordingcondition on the optical disk 500, is determined, and the strategy isconverted into recording pulses by a pulse generating circuit 300. Then,the recording pulses are output to an LD driver 124.

The LD driver 124 drives the laser diode 110 based on the inputrecording pulses, and the laser diode 110 controls an output laser beamcorresponding to the recording pulses, such that the controlled laserbeam is irradiated onto the optical disk 500, rotating at a constantlinear velocity or a constant rotation speed, through a collimator lens112, a diffraction grating 114, a half mirror 116, and an object lens118, which allows recording patterns composed of pit and space stringscorresponding to the desired record data to be recorded on the opticaldisk 500.

On the other hand, when the information recorded on the optical disk 500is reproduced, a reproducing laser beam emitted from the laser diode 110is irradiated onto the optical disk 500 through the collimator lens 112,the diffraction grating 114, the half mirror 116, and the object lens118.

At that time, the intensity of the reproducing laser beam is lower thanthat of the recording laser beam, and the reflected light of thereproducing laser beam from the optical disk 500 travels to a detector122 through the object lens 118, the half mirror 116, and a receiverlens 120 and is then converted into an electric signal.

The electric signal output from the detector 122 corresponds to therecording pattern composed of pits and spaces recorded on the opticaldisk 500 and is digitized into binary numbers by a slicer 210. Then, thedigitized signal is decoded into a reproduction signal by the EFMencoder/decoder 216 to be output.

FIG. 2 is an exploded perspective view illustrating the structure of apick-up unit incorporated into the drive shown in FIG. 1. As shown inFIG. 2, two diffraction gratings 114-1 and 114-2 are provided betweenthe laser diode 110 and the optical disk 500, and grooves 115-1 and115-2 formed in different directions are formed on the diffractiongratings 114-1 and 114-2, respectively.

When a laser beam 20 is irradiated onto the diffraction gratings havingthe above-mentioned structure, the laser beam is divided into threelaser beams by the first diffraction grating 115-1, and one of thedivided laser beams is further divided into three laser beams by thesecond diffraction grating 115-2. As a result, five spots 20A to 20E areirradiated onto the optical disk 500.

FIG. 3 is a plan view illustrating the landing positions of the spotsirradiated onto the optical disk. As shown in FIG. 3, a main beam 20Afor recording, a leading sub-beam 20B for tracking, a succeedingsub-beam 20C for tracking, a leading sub-beam 20D for reproduction, anda succeeding sub-beam 20E for reproduction are irradiated onto theoptical disk 500.

Here, the main beam 20A for recording is irradiated onto a groove 502-2formed on the optical disk 500, which allows a pit 506 to be formed inthe groove 502-2. This main beam 20A for recording is set to have thehighest light-emitting intensity so that the pits are formed through aheat mode.

The leading sub-beam 20B for tracking is irradiated onto a land 504-3adjacent to the groove 502-2 onto which the main beam 20A is irradiated,and the succeeding sub-beam 20C for tracking is irradiated on a land504-2 that is adjacent to the groove 502-2 onto which the main beam 20Ais irradiated and that is opposite to the land 504-3 onto which thesub-beam 20B is irradiated.

The leading sub-beam 20D for reproduction is irradiated to precede themain beam 20A in a position, onto the same groove 502-2 where the mainbeam 20A is irradiated, and the succeeding sub-beam 20E for reproductionis irradiated to succeed the main beam 20A in a position, onto the samegroove 502-2 where the main beam 20A is irradiated.

The positions of the respective spots located in this way make itpossible to detect the recording pattern formed by the main beam 20A,that is, the recording pattern composed of a combination of the pit 506and the space 508, using the succeeding sub-beam 20E for reproduction.

FIG. 4 is a conceptional view illustrating the relationships between thedetector and the spots irradiated onto the optical disk. As shown inFIG. 4, the detector 122 shown in FIG. 1 has five optical receivingparts 122A to 122E, and reflected light components 22A to 22Ecorresponding to the spots 20A to 20E are respectively irradiated ontothe optical receiving parts and are then converted into electricsignals.

FIGS. 5A to 5E are conceptional views illustrating the relationshipsbetween the waveform of a recording pulse and a stable area. As shown inFIGS. 5A to 5E, the recording pluses having various waveforms are outputfrom the LD driver 124 shown in FIG. 1, and each recording pulseincludes a high output segment 50 indicating an ON state of therecording pulse, a low output segment 52 indicating an OFF state of therecording pulse, and a constant output portion 54 in which the recordingpulse is in the ON state and little modulation occurs.

More specifically, FIG. 5A shows a recording pulse that is in an ONstate and has a fixed output, and FIG. 5B shows a recording pulse havingdifferent amplitudes at a head part and a rear part. FIG. 5C shows arecording pulse having different amplitudes at a head part, a middlepart, and a rear part, respectively, and FIG. 5D shows a recording pulsein which a fixed output portion is formed at a head part and thenoutputs are changed several times at a rear part.

In the present invention, it is intended that the reproduction signal beacquired in a state in which the recording pulse turns to an ON state.Therefore, it is preferable to generate a gate signal, which will bedescribed in detail later, to correspond to the high output segment 50,and it is more preferable to generate the gate signal to correspond tothe constant output portion 54 which is not easily affected bymodulation. The constant output portion 54 is defined as a portion ofthe high output segment 50 that has a long interval and is in the moststable state. Alternatively, an area having a stable state shorter thanthat having the longest stable state can be used as the constant outputportion. In addition, in the present embodiment, the pulse waveformshown in FIG. 5C, called a castle-type waveform, is given as an example.However, the invention can be applied to other recording pulses.

For example, it is preferable that, when the invention is applied to arecording power used for a phase change-type optical disk as shown inFIG. 5C, the gate signal be generated to correspond to the constantoutput portion 54 corresponding to deletion power, among the recordingpulses composed of the high output segment 50 that becomes an amorphousstate by repeatedly performing the high output and the low output torapidly cool down a phase-change material, the low output segment 52outputting a sufficient amount of power to perform servo control withthe main beam, for example, a power of about 0.7 to 1 mW, and theconstant output portion 54 that is turned to a crystal state by slowcooling, and that signals reproduced by the sub-beams be input to theconstant output portion 54.

FIG. 6 is a circuit block diagram illustrating the internal structure ofthe pulse generating circuit shown in FIG. 1. As shown in FIG. 6, in thepulse generating circuit 300, the strategy conditions SD1 and SD2 outputfrom the CPU 212 shown in FIG. 1 are transmitted to pulse unitgenerating circuits 310-1 and 310-2, respectively, to generate pulsesignals PW1 and PW2 in synchronization with a clock signal CLK.

Here, the strategy conditions SD1 and SD2 are defined as numerical datain which the length of a period for which the pulse is in an ON stateand the length of a period for which the pulse is in an OFF state areindicated by the number of clocks. The pulse unit generating circuits310-1 and 310-2 having received the data generate pulse signals havingconditions represented by the strategy conditions SD1 and SD2, using theclock signal CLK generated in the drive.

These pulse signals PW1 and PW2 are output to the LD driver 124 shown inFIG. 1, and the logical multiplication of an inversion signal of thepulse signal PW1 and the pulse signal PW2 is calculated by an ANDcomputing unit 316. Then, the logical multiplication is output to a maskcircuit 400 shown in FIG. 1 as a gate signal Gate. Here, an inversionsignal of the pulse signal PW1 is generated by an inverting circuit 314.

FIGS. 7A to 7E are timing charts illustrating the generation principalof the gate signal shown in FIG. 6. As shown in FIGS. 7A to 7E, the gatesignal corresponding to the constant output portion of the recordingpulse is generated using the pulse signals PW1 and PW2 constituting therecording pulse. That is, as shown in FIGS. 7B and 7C, the pulse signalsPW1 and PW2 are generated in synchronization with the clock signal CLKshown in FIG. 7A, and the inversion signal shown in FIG. 7D is generatedfrom the pulse signal PW1.

Further, when the levels of the pulse signal PW2 in FIG. 7C and theinversion signal thereof in FIG. 7D are defined as shown in FIGS. 7C and7D, respectively, the logical multiplication thereof is calculated, sothat the gate signal shown in FIG. 7E is obtained. As a result, the gatesignal obtained in this way corresponds to the constant output portionof the recording pulse.

FIG. 8 is a circuit diagram illustrating the internal structure of theLD driver shown in FIG. 1. As shown in FIG. 8, the LD driver 124includes voltage dividing circuits respectively using resistors R1 andR2 and a synthesizing unit 126 for synthesizing voltages output fromthese voltage dividing circuits, and the pulse signals PW1 and PW2 fromthe pulse generating circuit 300 are amplified to predetermined outputlevels by the resistors R1 and R2, respectively. Then, the synthesizingunit 126 calculates the logical sum of the amplified signals to generatea recording pulse PWR, and the recording pulse PWR is output to thelaser diode 110 shown in FIG. 1.

FIG. 9 is a circuit block diagram illustrating the internal structure ofthe mask circuit shown in FIG. 1. As shown in FIG. 9, the mask circuit400 includes two AND computing units 410-1 and 410-2. The gate signalGate generated by the pulse generating circuit 300 shown in FIG. 1 and aflag signal Flag generated by the CPU 212 shown in FIG. 1 are input tothe first-stage AND computing unit 410-1. Then, the AND computing unit410-1 calculates the logical multiplication of these signals to generatea gate signal Gate′ and outputs it to the AND computing unit 410-2 inthe next stage thereof.

The AND computing unit 410-2 puts a mask on an RF signal RF-Subreproduced by the succeeding sub-beam 20E for reproduction that isoutput from the detector 122E shown in FIG. 4, using the gate signalGate′, to extract an RF signal RF-Sub′ corresponding to the gate signalGate′, and then outputs it to the slicer 210 shown in FIG. 1. As aresult, the RF signal RF-Sub′ reproduced in the constant output portionof the recording pulse is selectively extracted, which enableshigh-precision pit detection.

Then, the CPU 212 shown in FIG. 1 calculates the correction conditionsof strategy, based on the length or phase information of the detectedpit and performs correction on the strategy conditions to be output tothe pulse generating circuit 300. As a result, real time correction inwhich recording conditions are corrected during the recording of data isperformed.

FIGS. 10A to 10F are timing charts illustrating the relationships amonga recording pulse, a gate pulse, and a reproduction signal. As shown inFIG. 10A, the recording pulse PWR is a pulse pattern whose ON or OFFstate is changed so as to correspond to a predetermined data pattern.Here, assuming that the constant output portion 54 of a pit 14T havingthe longest non-modulation area is used as a gate signal, the gatesignal Gate generated by the pulse generating circuit 300 shown in FIG.1 is output at the timing shown in FIG. 10B, and the flag signal Flaggenerated by the CPU 212 shown in FIG. 1 is output at the timing shownin FIG. 10C. In addition, the gate signal Gate′ generated by the maskcircuit 400 shown in FIG. 9 is output at the timing shown in FIG. 10D.Further, the RF signal RF-Sub′ shown in FIG. 10F is extracted from theRF signal RF-Sub shown in FIG. 10E using the gate signal Gate′.

As such, since the finally extracted reproduction signal RF-Sub′ is asignal reproduced in the constant output portion 54 of the recordingpulse PWR, this signal enables the high-precision detection of pits andthe accurate correction of strategy.

FIG. 11 is a conceptional view illustrating a generating process of theflag signal executed by the CPU shown in FIG. 1. More specifically, FIG.11 shows an example in which a space 4T existing in the constant outputportion of the pit 14T is selectively detected. As shown in FIG. 11, theCPU 212 sequentially stores numerical values corresponding to the datalength of the recording pulse in a memory 214, specifies data whosespace 4T (which is represented by ‘L4’ in FIG. 11) exists in theconstant output portion of the pit 14T (which is represented by ‘P 14’in FIG. 11), and raises a flag to the specified data of the pit 14T.

Here, when a time difference between the main beam for recording and thesub-beam for reproduction is ‘τ’ the CPU 212 compares the length of dataexisting between the pit 14T and the space 4T with the time differenceτ, converting the time difference τ into the number of clocks. As theresult of comparison, when the data of the space 4T exists in a regionspaced apart from the pit 14T by the time difference τ and in a rangecorresponding to the constant output portion of the pit 14T, the CPU 212raises a flag to the pit 14T and then outputs the flag signal Flag atthe timing shown in FIG. 10.

FIGS. 12A to 12E are timing charts illustrating the relationshipsbetween the main beam for recording and the sub-beam for reproduction.As shown in FIG. 12A, the output of the main beam for recording becomesa high-output pulse pattern required for forming a pit, and a pitpattern formed on the optical disk by irradiating this pulse becomes asshown in FIG. 12B.

On the other hand, as shown in FIG. 12C, the output of the sub-beam forreproduction becomes a pulse pattern having a lower output than the mainbeam for recording by a branching ratio, at the same timing as that ofthe output pattern of the main beam for recording. In addition, a pitpattern reproduced by the sub-beam for reproduction is a pattern delayedfrom the pit during recording by the time difference τ, as shown in FIG.12D.

Therefore, when the space 4T reproduced during the recording of the pit14T is detected, it is preferable to specify a position where the space4T of a pulse obtained by delaying the pattern of the recording pulse bythe time difference τ overlaps the constant output portion of the pit14T of the recording pulse, as shown in FIG. 12E. That is, the followingstructure is useful: a first gate signal is generated from a constantoutput portion having a long pit in the recording pulse, a second gatesignal is generated from a pulse corresponding to a short pit or space,which is a detection target, of a pulse pattern obtained by delaying therecording pulse by the time difference τ, and a mask is put on the RFsignal obtained from the sub-beam for reproduction, using the first andsecond gate signals.

FIGS. 13A to 13G are timing charts illustrating the relationships amonga recording pulse, a pulse obtained by delaying the recording pulse, andan RF signal. As shown in FIGS. 13A to 13G, a pulse PWR′ is generated bydelaying the recording pulse PWR by the time difference τ. In this case,when a portion of the delayed pulse PWR′ in which the space 4T isincluded is the gate signal Gate′ in the constant output portion of thepit 14T of the recording pulse PWR, it is possible to selectively detecta short pit or space while a long pit is being recorded, which makes itpossible to accurately detect the length or phase variation of a pit.

FIG. 14 is a block diagram illustrating an example of a process ofdetecting a short pit or space while a long pit is being recorded.Specifically, FIG. 14 shows a structural example in which the EFMencoder/decoder 216 shown in FIG. 1 detects a 4T space existing underthe sub-beam while the main beam records a 14T pit.

In the above-mentioned structure, as shown in FIG. 14, the EFMencoder/decoder 216 temporally stores a binary signal of 8 bits inputfrom the slicer 210 shown in FIG. 1 in a buffer 250-1, and converts the8-bit data output from the buffer into 16-bit data according to aconversion table 252 to output it to a buffer 250-2. At that time, adelay operation of a time T by a delay unit 254 is performed for everyconversion.

The data stored in the buffer 250-2 is output to a counter 256. Then,the data is output from the counter to the pulse generating circuit 300via the CPU 212 shown in FIG. 1 as data indicating a pulse length nT(where n is a natural number in the range of 3 to 14), so that thecorresponding recording pulse is generated.

FIG. 15 is a block diagram illustrating the relationships between thecounter 256 shown in FIG. 14 and the pulse generating circuit 300 shownin FIG. 1. As shown in FIG. 15, the counter 256 has a 14T decoder 258for specifying a bit string corresponding to a 14T pit of a data streamflowing from the buffer 250-2 to the pulse generating circuit 300 and a4T decoder 259 for specifying a bit string corresponding to a 4T space.

FIGS. 16A to 16C are conceptual views illustrating an example in whichthe buffer 250-2 shown in FIG. 14 stores a bit string. As shown in FIG.16C, data indicating the length of a pit or space in synchronizationwith a clock signal shown in FIG. 16A is stored in the butter 250-2.

For example, the length of 3T is represented by a binary number ‘100’,and the length of 4T is represented by a binary number ‘1000’. Inaddition, the length of 5T is represented by a binary number ‘10000’,and the length of 14T is represented by a binary number‘10000000000000’.

Therefore, when a pulse shown in FIG. 16B is input, in the bit stringstored in the buffer 250-2, a part corresponding to a 4T space is ‘1000’in binary number, and another part corresponding to a 14T pit is‘10000000000000’ in binary number, as shown in FIG. 16C. That is, therespective pulse widths are stored in a bit number format.

Here, when a gap between the main beam for recording and the sub-beamfor reproduction corresponds to 300 bits, as shown in FIG. 16C, theposition of the 14T pit currently being recorded is specified from thebit string stored in the buffer 250-2, and it is determined whether thebit string of the 4T space is located at a position spaced apart fromthe 14T pit by 300 bits.

As a result, when the bit string of the 4T space is located at thatposition, that point of time is determined as the timing when the 4Tspace can be detected by the sub-beam during the recording of the 14Tpit by the main beam, and the conditions of real time correction aredetermined using a signal obtained at that timing.

FIGS. 17A to 17C are conceptual views illustrating the variation of the4T space, which is a detection target during the recording of the 14Tpit. As shown in FIG. 17A, when the recording pulse of the 14T pit iscomposed of a 3T pulse having a high output, a 9T pulse having a stableoutput, and a 2T pulse having a high output, a 4T space in the stableoutput area becomes a detection target.

Therefore, it is the most preferable to extract the 4T space appearingat the center of the 14T pulse. However, since the appearanceprobability of the 4T space is low at that position, the counter circuitis provided such that the 4T space becomes a detection target even ifboth ends of the 4T space are in the stable output area of the 14T pit.

For example, a gate signal shown in FIG. 17B is generated from a pulseof the 14T pit shown in FIG. 17A, and a data pattern capable ofspecifying the 4T space included in the gate signal, which is a hatchedpotion in FIG. 17C, is prepared. Then, a bit string corresponding tothis data pattern is extracted.

FIG. 18 is a block diagram illustrating another example of the processof detecting a short pit or space during the recording of a long pit.Specifically, FIG. 18 shows an example in which it is determined whetherthe short pit or space exists during the recording of the long pit,based on the number of pulses generated for a certain period of time.

In a circuit block shown in FIG. 18, a binary signal SL RF-Sub′ outputfrom the slicer 210 is input to an AND computing unit 422 via aninverting circuit 420-1, and the gate signal Gate output from the pulsegenerating circuit 300 shown in FIG. 1 is also input to the ANDcomputing unit 422.

The AND computing unit 422 calculates the logical multiplication of theinput signals and outputs it to a set terminal of a counter 424. Then,the counter 424 having received the signal counts the number of pulsesthat are generated within the period of time indicated by the gatesignal inverted by an inverting circuit 420-2 and outputs the countresult to the CPU 212 shown in FIG. 1 as a determination signalDetection Enable. In addition, the gate signal inverted by the invertingcircuit 420-2 is used as a reset signal of the counter 424.

The CPU 212 determines whether the 4T space exists during the recordingof the 14T pit, based on whether the number of pulses indicated by thedetermination signal is a predetermined number or more, for example, twoor more. As a result, when it is determined that the 4T space exists,the CPU 212 performs the fetch of a signal obtained from the 4T space.

FIGS. 19A to 19G are timing charts illustrating an example of a processexecuted by the circuit block shown in FIG. 18. As shown in FIG. 19A, asignal RF-Sub′ input to the slicer 210 is digitized into a binary numberat a certain level, so that a pulse signal SL RF-Sub′ shown in FIG. 19Bis generated.

Further, the determination signal Detection Enable shown in FIG. 19G isgenerated by calculating the logical multiplication of the gate signalGate shown in FIG. 19E that is generated from the signals shown in FIGS.19C and 19D by the pulse generating circuit 300 shown in FIG. 1 and theinversion signal shown in FIG. 19F that is generated by the invertingcircuit 420-1.

FIGS. 20A to 20D are conceptual views illustrating a determinationreference of the determination signal generated by the circuit blockshown in FIG. 18. As shown in FIGS. 20A to 20D, when two or more pulsesare counted within the interval shown in FIG. 20A, it is determined thatthe space included in the gate signal Gate indicating the stable area of14T, for example, a space of 3T to 7T, exists during the recording ofthe 14T pit, and the CPU 212 performs the fetch of the signal obtainedfrom the 4T space.

Therefore, as shown in FIG. 20B, when two pulses are counted in the gatesignal, it is determined that the space included in the gate signal Gateindicating the stable area of 14T, for example, a space of 3T to 7Texists during the recording of the 14T pit, and the signal obtained fromthe 4T space is fetched. On the other hand, as shown in FIGS. 20C and20D, when only one pulse is counted, it is determined that the 4T spacedoes not exist during the recording of the 14T pit, so that the fetch ofa signal is not performed.

FIG. 21 is a block diagram illustrating still another example of theprocess of detecting a short pit or space during the recording of a longpit. Specifically, FIG. 21 shows an example in which it is determinedwhether a short pit or space exists during the recording of a long pitby measuring the length of the pulse generated in the gate signal.

In the circuit block shown in FIG. 21, the AND computing unit 422calculates the logical multiplication of the binary signal SL RF-Sub′output from the slicer 210, the gate signal Gate output from the pulsegenerating circuit 300 shown in FIG. 1, and the clock signal CLK, andthen outputs the logical multiplication thereof to a set terminal of thecounter 424 as a countable signal Countable Pulse. Then, the counter 424calculates the length of the countable signal. In addition, a resetpulse generated by a reset pulse generating circuit 426 is input to thecounter.

FIGS. 22A to 22E are timing charts illustrating an example of a processexecuted by the circuit block shown in FIG. 21. As shown in FIG. 22A,the signal RF-Sub′ input to the slicer 210 is digitized into a binarynumber at a certain level, so that the pulse signal SL RF-Sub′ shown inFIG. 22B is generated.

Therefore, the countable signal Countable Pulse shown in FIG. 22E isgenerated by the logical multiplication of the gate signal Gate shown inFIG. 22C that is generated by the pulse generating circuit 300 shown inFIG. 1 and the clock signal CLK shown in FIG. 22D. Here, the clocksignal whose 1T is equal to one period is used. However, a high-speedclock whose 1T is equal to 40 periods, for example, may be used toimprove the resolution of length detection.

FIGS. 23A to 23D are timing charts illustrating an example of theoperation of the reset pulse generating circuit 426 shown in FIG. 21. Asshown in FIGS. 23A to 23D, the reset pulse generating circuit 426 countstwo clock signals CLK shown in FIG. 23A at one time to generate a middlesignal CLK/2 shown in FIGS. 23B and counts two middle signals CLK/2 atone time to generate a middle signal CLK/4 shown in FIG. 23C.

Further, as shown in FIG. 23D, the reset pulse generating circuit 426generates a reset signal Reset that rises in synchronization with thesecond rising of the middle signal CLK/4 shown in FIG. 23C and thatfalls when a length corresponding to the gate signal Gate is scanned.The reset signal is input to the reset terminal of the counter 424 shownin FIG. 21 to reset the count result of the counter.

Furthermore, when a signal whose 1T is equal to 40 periods is used asthe clock signal shown in FIG. 23A, and when the gate signal Gate has awidth corresponding to 9T, the reset signal Reset shown in FIG. 23Dfalls when the clock signal is counted 360 times, so that the counter424 is reset.

Similarly, when a signal whose 1T is equal to 2.5 periods is used as theclock signal shown in FIG. 23A, and when the gate signal Gate has awidth corresponding to 9T, the reset signal Reset shown in FIG. 23Dfalls when the clock signal is counted 22.5 times, so that the counter424 is reset. However, when the period of the clock signal is not anintegral multiple of a unit length T, such as ‘1T=2.5 periods’, it istreated as an integral multiple, such as ‘2T=5 periods’.

INDUSTRIAL APPLICABILITY

According to the invention, real time correction can be performed withhigh precision. Therefore, the invention can be applied to recordingenvironments in which recording conditions vary at the inner or outercircumference of an optical disk.

1. An optical information recording device that records information onan optical recording medium by pulse irradiation of a recording laserbeam onto the optical recording medium and that detects the informationby irradiating a reproduction laser beam onto the optical recordingmedium, wherein pulse irradiation of the recording laser beam isperformed with a recording pulse having at least a high output segmentand a low output segment pulse irradiation of the reproduction laserbeam is performed at a timing synchronized with the pulse irradiation ofthe recording laser beam, and detection of information is performedduring the high output segment and/or a constant output portion of therecording laser beam and/or the reproduction laser beam.
 2. An opticalinformation recording device that records information on an opticalrecording medium by pulse irradiation of a recording laser beam onto theoptical recording medium and that detects the information by irradiatinga reproduction laser beam onto the optical recording medium, wherein therecording laser beam and the reproduction laser beam are branched from acommon laser beam, comprising: a pulse generating unit that generates arecording pulse having at least a high output segment and a low outputsegment; and a mask unit that masks a reproduction signal obtained bythe irradiation of the reproduction laser beam during the high outputsegment and/or a constant output portion of the recording pulse.
 3. Anoptical information recording device that records information on anoptical recording medium by pulse irradiation of a recording laser beamonto the optical recording medium and that detects the information byirradiating a reproduction laser beam onto the optical recording medium,wherein the recording laser beam and the reproduction laser beam arebranched from a common laser beam, comprising: a pulse generating unitthat generates a recording pulse having at least a high output segmentand a low output segment; a gate signal generating unit that generates agate signal during the high output segment of the recording pulse; aunit that specifies a time difference between the recording laser beamand the reproduction laser beam illumination of the same location on theoptical recording medium; a unit that specifies a detection target pulsehaving a length shorter than the gate signal; and a detecting unit thatacquires a reproduction signal obtained by the irradiation of thereproduction laser beam at the timing the detection target pulse isincluded in the gate signal in consideration of the time difference. 4.An optical information recording device that writes information on anoptical recording medium by pulse irradiation of a recording laser beamonto the optical recording medium and that detects the information byirradiating a reproduction laser beam onto the optical recording medium,wherein the recording laser beam and the reproduction laser beam arebranched from a common laser beam, comprising: a pulse generating unitthat generates a recording pulse by calculating the logical sum of afirst pulse and a second pulse; a unit for pulse irradiation of therecording laser beam during the recording pulse; a gate pulse generatingunit that generates a gate pulse by calculating the logicalmultiplication of the second pulse and an inversion of the first pulse;and a detecting unit that acquires a reproduction signal obtained by theirradiation of the reproduction laser beam during the gate pulse.
 5. Anmethod of recording information on an optical recording medium by pulseirradiation of a recording laser beam on the optical recording mediumand of detecting the information by irradiating a reproduction laserbeam onto the optical recording medium, comprising: irradiating theoptical recording medium with a recording pulse having at least a highoutput segment and a low output segment; and detecting the informationduring a high output segment and/or a constant portion of the recordinglaser beam.